Answer to Tomservo

High Efficiency Speaker Asylum

Need speakers that can rock with just one watt? You found da place.

Hi Tom,
I finally saw your post from 10/23, but that thread is about to fall off the page. So, I thought I'd move the discussion up a bit. You said:
Hi
A few questions, if I can ask.
What properties would a bass compression driver like this have?
How high and low does it go?
How much acoustic power does it need to produce?
An interesting topic.
Tom Danley
Tom, I'm afraid that I have more questions than answers myself at this point, but would really appreciate any input you have on this subject. Our goal is develop drivers and horns that are optimized for hi fi use. I suppose it would be good to have a device that develops perhaps 115dB peak SPLs into a medium to large living room with linearity and low distortion. My math is a little shaky, but it looks to me like it would require about 30W of input to accomplish this. I would hesitate to shoot for higher output though, if it meant bulking up the moving system to withstand higher power inputs.
We haven't done much testing yet on our first bass compression drivers yet aside from from frequency response measurements taken outside with a handheld 1/3 octave RTA. Results were encouraging, with average sensitivity of 107dB/1W/1M from 70 to 600Hz. and a long, gentle downslope from there up. I've never seen a curve quite like it- almost straight as a ruler up to 10kHz., where sensitivity is down to about 90dB/1W/1M. It drops more rapidly from there up.
Our biggest surprise was in discovering that the bass driver and horn make a quite decent wide band system when fed a full range signal. The highs are recessed to be sure, but sound good. There are no particular break up peaks or other nastiness, and vocals sound about as good as they do from our midrange driver. Makes me wonder what could be done with a design with maybe an aluminum coil and a phasing plug that attempts to scavenge highs.
The low end of this driver/horn combination is down 6dB by 63Hz. in the far field and drops rapidly below that. I think this is mostly the horn cutoff (50Hz. exponential) kicking in, and the 7 square foot mouth losing control of the pattern.
We haven't done plane wave tests on the bass driver yet. Our midrange driver, with its smaller but similar center-suspended carbon fiber cone diaphragm, looks scary good on the low end on a PWT. It shows a small bump at the 125Hz. cone resonance, but remains basically flat to 50Hz. and is only down 8 or 10dB at 10Hz. An Altec 290E I tested for comparison rolls off more steeply below 200Hz., but its diaphragm is more stiffly suspended and excursion limited.

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Topic - Answer to Tomservo - Steve Schell 11:25:42 10/27/05 (10)

Re: Answer to Tomservo - tomservo 11:52:10 10/30/05 (5)

Re: Answer to Tomservo - Steve Schell 22:46:04 11/01/05 (4)

Re: Answer to Steve & driver stuff - tomservo 18:06:08 11/03/05 (3)

Candidate drivers based on ideal specs - PK 23:03:29 11/04/05 (2)

Re: Candidate drivers based on ideal specs - tomservo 17:12:34 11/06/05 (1)

Re: Candidate drivers based on ideal specs - PK 00:38:54 11/07/05 (0)

Re: I have a question. - Dave-A 20:42:22 10/27/05 (3)

Re: I have a question. - Steve Schell 00:34:22 10/28/05 (2)

Find a corner... - Mark Seaton 09:04:02 10/28/05 (1)

Re: Find a corner... - Steve Schell 22:51:18 11/01/05 (0)

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